The identification and clinical utilization of parasite derived antigens remains a major goal of the laboratory. PSAP, a glycoprotein obtained from adult S. mansoni was purified by means of column and lectin chromatography. Labeled PSAP was utilized to measure IgM and IgG responses. In defined groups of patients acute infection could be differentiated from chronic infection by the predominate IgM responses when compared to total antibody responses. Giardia lamblia following labeling with either Iodogen or lactoperoxidase secrete about 70% of the label into the culture media after about 24 hours. Identification of the secreted products is continuing. Excretory-secretory products of B. malayi were used to define antibody responses in infected patients.